Senate Minority Leader Mitch McConnell and many of his rank and file are poised to cast votes this week that will effectively rebuke Sen. Ted Cruz's effort to filibuster a stopgap spending bill that would keep the government funded past Sept. 30.

But a GOP-led filibuster puts many Republicans in the tough spot of opposing a bill they actually support while also likely causing a government shutdown. Any vote to filibuster is likely to come before Reid moves to strike the Obamacare defunding language.

“Sen. McConnell supports the House Republicans’ bill and will not vote to block it, since it defunds Obamacare and funds the government without increasing spending by a penny. He will also vote against any amendment that attempts to add Obamacare funding back into the House Republicans’ bill,” said Don Stewart, spokesman for the Kentucky Republican. “If and when the Majority Leader goes down that path, Washington Democrats will have to decide — without hiding behind a procedural vote — whether or not to split with their leadership and join Republicans and their constituents in opposing the re-insertion of Obamacare funding into the House-passed bill.”

Sen. Lindsey Graham, a South Carolina Republican who is up for re-election and faces a tea party challenge, didn't mince words about the problem with the tactics being employed by his fellow GOP senators.

"I think we'll take up the House bill because it's a good bill. I can't imagine filibustering the bill that I like from the House. There will be a vote to take out the defunding of Obamacare. It will be a majority vote," Graham said Monday on Fox News. "And I'm hoping some Democrats will side with all Republicans to keep the defunding in place, but I doubt it."

"It is our obligation to our constituents to do everything we can to prevent the majority leader from funding Obamacare with just 51 votes. Any member of this body that votes for cloture on this bill will be voting to allow the majority leader to fund Obamacare on 51 votes," Cruz said. "I think that vote's a mistake."

Reid shot that down quickly, even though Cruz's objective was plain: to bait the majority leader into objecting so he could accuse Democrats of causing any subsequent government shutdown.

But beyond worrying about the wisdom of causing a government shutdown over Obamacare, some Senate Republicans are also grumbling that the Texas Republican and his allies have picked the wrong fight and should be pushing to lower the $986 billion spending cap included in the House bill.

Some Senate Republicans do not support the underlying House bill but may vote with Democrats against a filibuster — a situation that has made the expected test vote harder to predict.

For example, Sen. Tom Coburn, who has argued that Republicans should insist on a post-sequester spending level of $967 billion for the next fiscal year, said Sunday that Cruz and his colleagues are distracting from what should be "the real focus."

"So the real issue is we're not talking about something that Republicans can win on, which is, for the first time since the end of the Korean War we will have actually decreased discretionary spending in this country two years in a row, which is a real achievement, and we haven't even touched the surface of the waste and fraud that is out there," the Oklahoma Republican said on CBS' "Face the Nation."

Coburn has an assortment of like-minded lawmakers on the funding question. Six senators joined with Coburn and Sen. Jeff Flake, R-Ariz., on a letter calling on Reid to put a CR at the $967 billion level.

What has frustrated some dedicated fiscal conservatives is that a few tea-party-affiliated groups have conceded in private correspondence with other conservatives that they're less concerned with spending levels than about cutting funding for Obamacare. Tea Party Patriots is one such group, demonstrating a commitment to the defunding effort at the expense of having the broader spending debate.

There are groups siding with Coburn and company, however. The National Taxpayers Union, for instance, sent a letter to senators last week highlighting what they view as the importance of the $967 billion spending level.

"Attempts by Congress to peg spending above this level would result in the Office of Management and Budget (OMB) issuing a sequester order within 15 days of the end of the current session. While it is true that taxpayers might yet achieve the savings they so urgently need, temporarily postponing the cuts and relying on the sequestration mechanism would give government agencies less time to adjust to the spending limits imposed by the law," NTU Vice President Brandon Arnold wrote.

One Republican aide not aligned with Cruz or Coburn said that senators in both camps will have the opportunity to define their votes on that big test vote that's expected to come Friday. Of course, Republican aides expect Reid to use a procedural maneuver called "filling the amendment tree" to prevent Coburn or anyone else from offering amendments to reduce the funding level.